The present invention relates to the field of environmental protection technology and, more particularly, to a novel method for proceeding with sludge supersonic pre-treatment and controlling the pH value during sludge anaerobic treatment to significantly reduce the release amount of resistance genes that are common in residual sludge and supernatant liquid.
It is known that the use of antibiotics achieves an important effect in controlling infectious diseases. However, the abuse of antibiotics in recent decades causes mass propagation of resistant microorganisms and wide spread of resistance genes. Extensive research results have confirmed that sewage treatment plants receiving various waste waters have become the serious pollution sources of resistance microorganisms and resistance genes. The resistance genes as new pollutants not only damage the eco-environment but become a threat to the human health through the food chain. The wide use of tetracycline and sulfonamide antibiotics causes detection of a large amount of tetracycline and sulfonamide resistance genes in sewage treatment plants. Taking tetracycline resistance genes as an example, the concentration in effluent of a sewage treatment plant can be up to 102-106 copies/mL, and the concentration in the excess sludge is as high as 108-109 copies/g. It is known that anaerobic treatment is an important way to recycle sludge. However, conventional anaerobic treatment cannot effectively reduce the resistance genes in the sludge. Thus, to minimize the potential impact to the environment from the resistance genes, it is necessary to develop an effective, novel technique to reduce release of resistance genes during sludge anaerobic treatment.
Currently, some researchers have achieved the goal of reduction of resistance genes in sludge by controlling the sludge treatment conditions. For example, research in recent years found that the reduction effect of resistance genes by sludge anaerobic treatment was better than aerobic treatment. Furthermore, the temperature control during the anaerobic treatment could affect removal of resistance genes from sludge. Thermophilic fermentation was advantageous to removal of certain resistance genes. However, mesophilic fermentation had limited influence on removal of some resistance genes. According to the research by the inventor, the transfer of resistance genes relied on extracellular DNA and phages that are potential carriers increasing horizontal gene transfer. On the other hand, the number of gene carriers for horizontal transfer could be significantly reduced by supersonic treatment and adjusting the pH value during the anaerobic treatment, thereby affecting the release level of resistance genes.